Earnings Per Common Share (Calculations) (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings per common share (attributable to PPG)
Continuing operations	$ 147	$ 392	$ 504	$ 328	$ 91	$ (211)	$ 339	$ 328	$ 1,371	$ 547	$ 1,311
Discontinued operations	0	217	(3)	6	253	27	31	19	220	330	95
Net income (attributable to PPG)	$ 147	$ 609	$ 501	$ 334	$ 344	$ (184)	$ 370	$ 347	$ 1,591	$ 877	$ 1,406
Weighted average common shares outstanding									256,100,000	265,600,000	271,400,000
Effect of dilutive securities:
Stock options									900,000	800,000	1,000,000
Other stock compensation plans									800,000	1,000,000	1,200,000
Potentially dilutive common shares									1,700,000	1,800,000	2,200,000
Adjusted weighted average common shares outstanding									257,800,000	267,400,000	273,600,000
Earnings per common share (attributable to PPG):
Continuing operations (in dollars per share)	$ 0.58	$ 1.53	$ 1.96	$ 1.28	$ 0.35	$ (0.79)	$ 1.26	$ 1.23	$ 5.35	$ 2.06	$ 4.83
Discontinued operations (in dollars per share)	0.00	0.85	(0.01)	0.02	0.96	0.10	0.12	0.07	0.86	1.24	0.35
Net Income (attributable to PPG) (in dollars per share)	0.58	2.38	1.95	1.30	1.31	(0.69)	1.38	1.30	6.21	3.30	5.18
Earnings per common share - assuming dilution (attributable to PPG)
Continuing operations (in dollars per share)	0.58	1.52	1.95	1.27	0.34	(0.79)	1.25	1.22	5.32	2.05	4.79
Discontinued operations (in dollars per share)	0.00	0.84	(0.01)	0.02	0.96	0.10	0.12	0.07	0.85	1.23	0.35
Net Income (attributable to PPG) (in dollars per share)	$ 0.58	$ 2.36	$ 1.94	$ 1.29	$ 1.30	$ (0.69)	$ 1.37	$ 1.29	$ 6.17	$ 3.28	$ 5.14
Outstanding stock options excluded from the computation of diluted earnings per share due to their antidilutive effect									600,000.0	600,000.0	600,000.0